This just happened to me again. A Collaborator marked a task as complete. This needs to be fixed ASAP.
I can confirm this beviours as well in Safari 10.1 Chrome 58 and Firefox 53 display fonts correctly in PDFs for review.
Yes! Definitely this. I've had jobs marked as Completed be changed to New by a Collaborator a few times. I love the Collaborators feature but I would love it even more if only a Regular User or Adm...